Can't tell from px, if you have to pull or move a valve to move the truck, then it has spring brakes, the objective is to stop all movement if one looses air pressure, usually on rear only, trains have them, same reason.

When sitting for a while, all air bleeds off, then no brakes. If need to move a 'dead' truck, bolt in middle of brake chamber allows 'cageing' of brakes for towing, etc. Most trucks with spring brakes no longer have parking brake.

If you can move it after sitting for a while, no spring brakes.

Ed

'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.